This is a note to let you know that I've just added the patch titled
cfq-iosched: fix locking around ioc->ioc_data assignment
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cfq-iosched-fix-locking-around-ioc-ioc_data-assignment.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <sta...@kernel.org> know about it.
>From ab4bd22d3cce6977dc039664cc2d052e3147d662 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jax...@fusionio.com>
Date: Sun, 5 Jun 2011 06:01:13 +0200
Subject: cfq-iosched: fix locking around ioc->ioc_data assignment
From: Jens Axboe <jax...@fusionio.com>
commit ab4bd22d3cce6977dc039664cc2d052e3147d662 upstream.
Since we are modifying this RCU pointer, we need to hold
the lock protecting it around it.
This fixes a potential reuse and double free of a cfq
io_context structure. The bug has been in CFQ for a long
time, it hit very few people but those it did hit seemed
to see it a lot.
Tracked in RH bugzilla here:
https://bugzilla.redhat.com/show_bug.cgi?id=577968
Credit goes to Paul Bolle for figuring out that the issue
was around the one-hit ioc->ioc_data cache. Thanks to his
hard work the issue is now fixed.
Signed-off-by: Jens Axboe <jax...@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gre...@suse.de>
---
block/cfq-iosched.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2704,8 +2704,11 @@ static void __cfq_exit_single_io_context
smp_wmb();
cic->key = cfqd_dead_key(cfqd);
- if (ioc->ioc_data == cic)
+ if (rcu_dereference(ioc->ioc_data) == cic) {
+ spin_lock(&ioc->lock);
rcu_assign_pointer(ioc->ioc_data, NULL);
+ spin_unlock(&ioc->lock);
+ }
if (cic->cfqq[BLK_RW_ASYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
Patches currently in stable-queue which might be from jax...@fusionio.com are
queue-2.6.39/block-add-req_secure-to-req_common_mask.patch
queue-2.6.39/cfq-iosched-fix-a-rcu-warning.patch
queue-2.6.39/cfq-iosched-fix-locking-around-ioc-ioc_data-assignment.patch
queue-2.6.39/cfq-iosched-make-code-consistent.patch
queue-2.6.39/block-use-the-passed-in-bdev-when-claiming-if-partno-is.patch
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